Science Projects And Inventions

YOU NEED:

• Two kitchen towel rolls
• A large cylindrical can 

Gingerly place one toilet paper roll on top of the other as shown in the top illustration. Rotate the top roll with your fingers along the table top.  As you would expect, the bottom roll rotates in the opposite direction and the two rolls travel together merrily.

This  time around change the top roll with a cylindrical can as in the illustration. Should you rotate the can, do you think the cardboard tube will move smoothly with the can or will it travel faster or slower than the can? The surprising thing is that the two companions travel as  if they were sized buddies.

HOW DOES IT WORK?

Simply the point of contact between the can and the tube travel on the same speed and cover the same distance. This has nothing to do with the sizes of the rolling objects.